In this talk, I shall present our recent ongoing work on  a model-agnostic reconstruction of the cosmic expansion history by combining DESI-DR2 BAO and DES-SN5YR data, with a focus on geometric determination of characteristic redshifts where notable tensions in the expansion rate are found to emerge. Employing Gaussian process regression alongside knot-based spline techniques, we reconstruct cosmic distances and their derivatives to pinpoint these characteristic redshifts and infer $E(z)= \frac{H}{H_{0}$. Our study reveals significant deviations of approximately 4 to 5 $\sigma$ from the Planck 2018 $\Lambda$CDM predictions, particularly pronounced in the redshift range $ z < 1$. These anomalies are consistently observed across both reconstruction methods and combined datasets, indicating robust late-time departures that could signal new physics beyond the standard cosmological framework.
 
The joint use of BAO and SN probes enhances the precision of our constraints, allowing us to isolate these deviations without reliance on specific cosmological assumptions. Our findings underscore the role of characteristic redshifts as sensitive indicators of expansion rate anomalies and motivate further scrutiny with forthcoming datasets from DESI-5YR BAO, Euclid, and LSST.




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Meeting ID: 989 3506 9843

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